Hydrogen selenide (H2Se) is a gas currently used in the photovoltaic industry for Copper Indium Gallium Selenide (CIGS) and Copper Indium Gallium Selenide Sulfide (CIGSS) thin film solar cells. Impurities in the H2Se gas may negatively affect the deposition process of the Se-containing films. Two such impurities include H2O and H2S. H2O may contribute oxygen to the metals being added to the film and hinder proper deposition. H2S may be added in a controlled manner later in the process. However, sulfur is known to change the bandgap structure of the selenium-containing adsorber layer, thus impurities such as H2S in H2Se may affect the film performance. The combination of H2S and H2O is known to cause corrosion of distribution systems and their components, leading to component/system failure as well as introduction of metal impurities during the deposition process resulting from corrosion of the distribution system.
Prior art gas purifiers are known in the art. See, e.g., the Nanochem® C/CL-series gas purifiers from Matheson Tri-Gas, the Mini Gaskleen® gas purifier from Pall Microelectronics, and the MC-190 and HP-190 MicroTorr purifiers from SAES Pure Gas, Inc. However, none of these purifiers identify H2Se as the gas to be purified and H2O and H2S as the impurities to be removed.
U.S. Pat. No. 4,797,227 to Tom et al. discloses a process and composition for purifying H2Se and H2Te to remove moisture and oxidant impurities therefrom. Tom et al. note that H2Se and H2Te are extremely difficult to purify because of their high reactivity and toxicity (col. 1, lines 35-37). Tom et al. utilize aluminum-containing compounds to remove water and oxidants from H2Se or H2Te (claim 1). The water and oxidants react with the aluminum-containing compounds (col. 5, lines 25-30). Tom et al. do not address the removal of H2S from H2Se.
JP2007-246342 to Taiyo Nippon Sanso Corp discloses a method for producing H2Se which has high purity and in which the water content and the amount of H2S are made particularly small. Taiyo Nippon Sanso Corp discloses the reaction of high purity H2 with metallic Se and liquefies or solidifies the resulting H2Se product. This process requires a lot of energy for both the reaction and the subsequent liquefaction/solidification.
A need remains for an efficient method to remove both H2O and H2S from available H2Se supplies.